1. Field
The present disclosure relates generally to wireless communications, and more specifically, to various systems and techniques for implementing packet data services with switched-circuit call notification.
2. Background
Modern communication systems are designed to allow multiple users to share a common communications medium. One such communications system is a code division multiple access (CDMA) system. CDMA is a modulation and multiple access scheme based on spread-spectrum communications. In a CDMA communications system, a large number of signals shares the same frequency spectrum and, as a result, provides an increase in user capacity. This is achieved by transmitting each signal with a different code that modulates a carrier, and thereby, spreads the signal over the entire spectrum. The transmitted signals can be separated in the receiver by a correlator using a corresponding code to de-spread the desired signal. The undesired signals, whose codes do not match, contribute only to noise.
CDMA modulation techniques have been standardized to facilitate interoperation between equipment manufacturers. By way of example, voice service using CDMA technology has been standardized in the United States in Telecommunications Industry Association TIA/EIA/IS-95-B, entitled “Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular Systems,” and referred to herein as “IS-95.” The IS-95 standard was originally optimized for transmission of voice over a circuit-switched network. Subsequent standards have built on the IS-95 standard to support a variety of additional non-voice services including packet data services. One such set of service options has been standardized in the United States in Telecommunications Industry Association TIA/EIA/IS-707-A, entitled “Data Service Options for Spread Spectrum Systems,” and referred to herein as “IS-707.” The IS-707 standard describes techniques for sending Internet Protocol (IP) packets through an IS-95 wireless network.
A CDMA standard supporting both voice and packet data services has been standardized in the United States in Telecommunications Industry Association (TIA), entitled “Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems, Release A—Addendum 1,” dated Oct. 27, 2000, and referred to herein as “cdma2000.” The initial release of cdma2000, however, did not provide for simultaneous use of both voice and packet data services. Consequently, a wireless communications device designed for this standard may not be able to receive an incoming circuit-switched call while supporting packet data services. This may be very undesirable in view of the fact that most voice calls today are circuit-switched. Many users would prefer to be notified of an incoming voice call so that they can decide whether to suspend packet data services and take the call. Alternatively, some users may prefer that the communications device itself be configured to automatically suspend packet data services in favor of an incoming voice call. In any event, there is a need in the art for an innovative approach to notify a wireless communications device of an incoming circuit-switched call while supporting packet data services in cdma2000 wireless devices. This approach should not be limited to this standard, but should be a broad-based solution applicable to wireless devices supporting various other communications standards.